The School of Basic Sciences at the Swiss Ecole Polytechnique Federale de Lausanne (EPFL) recommends transparent phosphate salt as a restrainer for lead from halide perovskite solar cells from getting absorbed by the soil when the solar panel stops working, breaks or gets wet.
Professor László Forró of EPFL calls it an ‘extremely important study’, for large scale commercialization of perovskite-based solar cells as the team expects this study to stimulate research, enabling lead halide perovskite solar cells to reach a similar environmental risk category as the commercially available, non-water-soluble heavy metal-containing CdTe and copper indium gallium diselenide (CIGS) technologies.
Lead, as is common knowledge, is not fit for human consumption and if it washes out into the soil, it can get into the human food chain and cause serious diseases. EPFL scientists call theirs an ‘elegant and efficient’ solution to prevent this from happening with the help of transparent phosphate salt.
It immediately reacts with lead to produce a water-insoluble compound that doesn’t leach out into the soil and can be recycled. What’s more, the researchers argue that transparent phosphate salt does not block sunlight or hamper the panel’s performance.
“We show that this approach can be used to build functional photodetectors, and we suggest that the broad community of researchers and R&D centers working on various devices like solar cells and light-emitting diodes implements it in their respective prototypes,” explained Pavao Andričević part of the research team.  
Their research work has been published in the scientific journal ACS Applied Materials & Interfaces as Fighting Health Hazards in Lead Halide Perovskite Optoelectronic Devices with Transparent Phosphate Salts.